The present invention relates to a massive aluminosilicate at least partly crystalline having an expanded closed cellular structure containing nitrogen, as well as the process for its manufacture.
An object of the present invention was to provide a novel expanded massive material having a good coefficient of thermal insulation, whilst possessing good compressive strength rendering it usable as a bearer material. Such a material finds multiple applications, both in the traditional field of building and in the thermal insulation of furnaces, in the manufacture of fireproof walls and doors, as well as in naval construction. "Massive" is used in the sense "monolithic", as opposed to "particulate".
It was also an essential object to be able to produce such a type of material which is light, impermeable to water, noninflammable and resistant to relatively high temperatures of the order of 1000.degree. C. In addition, it is highly desirable that such a material should be manufacturable continuously.
In the present state of the art, it is known to manufacture expanded glass foam materials by employing a technique of expanding reclaimed glass by means of carbonate which causes, by raising the temperature, a release of carbon dioxide. In practice, such a material does not however give entire satisfaction, particularly for the following reasons. Such a glass foam has a high sensitivity to moisture which may be attributed to the nature itself of the expansion agent used. In fact, the carbonates used allow the subsistence in the material of a metal oxide residue which is hydrolyzed in situ to give rise to basic lyes which are detrimental to the quality and the longevity of the product. The use of such a product therefore obligatorily necessitates an additional protection by means of a coating of a quality designed to ensure its impermeabilization.
In addition, such a glass foam can only be manufactured batchwise. Finally, its method of production necessitates a very long annealing time of the order of 17 hours, which of course has a very unfavorable influence on the production costs of such a product.
U.S. Pat. No. 2,837,873 has besides proposed a method of manufacturing a stratified vitreous material, having the form of a succession of layers of different cellular structures. The core of the material, of low density, which is intended to confer good thermal insulation, must however necessarily be jacketed by a denser layer if it is desired to obtain a product endowed with acceptable mechanical properties. The difference in cell structure of the successive layers results from a modification of the nature of the foaming agent used, the latter remaining in all the examples, still based on calcium carbonate. Such a product has also a high sensitivity to moisture, as mentioned previously. In addition, the compromise solution proposed by this U.S. Pat. No. 2,837,873 leads to a material whose properties, both insulating and mechanical, remain insufficient.